|
eyeglass lenses for you. Although not of a
quality useful for eyewear, these lenses are
very suitable for classroom use.
Bifocals and trifocals make fascinating
magnifying lenses. Fill a spherical glass
flask with water to make a lens. Water-filled
cylindrical glass or plastic bottles make
magnifiers that magnify in one direction
only. Aluminized mylar plastic stretched
across a wooden frame makes a good front
surface plane mirror. A Plexiglas mirror can
be bent to make a "funhouse" mirror. Low-reflectivity
plane mirrors can be made from a
sheet glass backed with black paper. Ask
the person in charge of audiovisual
equipment at the school to save the lenses
from any broken or old projectors that are
being discarded. Projector and camera
lenses are actually made up of many lenses
sandwiched together. Dismantle the lens
mounts to obtain several usable lenses.
Check rummage sales and flea markets for
binoculars and old camera lenses. A wide
assortment of lenses and mirrors are also
available for sale from school science
supply catalogs and from the following
organization:
Optical Society of America
2010 Massachusetts Avenue, NW
Washington, DC 20036
(202) 223-8130
|
For Further Research:
- Fill a long olive jar with water and place it
above a sign reading "CARBON
DIOXIDE." Use black ink to write
"CARBON" and red ink to write
"DIOXIDE." Support the jar with a rack cut
from a couple of small pieces of
cardboard. When the words are viewed
through the lens at the right distance,
carbon is inverted while dioxide is not.
Ask the students why this is so. Hint:
Both words are actually inverted.
- Use a baby moon hubcap as a convex
mirror. Aim a camera at the reflections on
the hubcap to take "fish-eye" pictures.
- A grazing-incidence mirror of the kind used
for infrared, ultraviolet, and x-ray
spacecraft can be simulated with a piece
of flexible reflective plastic such as a thin
mylar plastic mirror. Roll the plastic, with
its reflective surface inward, into a cone.
The small end of the cone should be open
so that you can look through it. Point the
cone like a telescope and look at a light
bulb several meters away. Adjust the
shape of the cone to increase the amount
of light that reaches your eye.
- Ask students to try to locate old lenses for
study as well as different objects that work
like lenses.
- Try to make a reflector telescope out of the
polished soft drink can in step 3. Compare
the curvature of the can's mirror with that
of a commercial reflector telescope. Why
is there a difference?
|
